Problem: Solve for $x$ and $y$ using substitution. ${-4x+4y = -12}$ ${x = 2y+11}$
Since $x$ has already been solved for, substitute $2y+11$ for $x$ in the first equation. ${-4}{(2y+11)}{+ 4y = -12}$ Simplify and solve for $y$ $-8y-44 + 4y = -12$ $-4y-44 = -12$ $-4y-44{+44} = -12{+44}$ $-4y = 32$ $\dfrac{-4y}{{-4}} = \dfrac{32}{{-4}}$ ${y = -8}$ Now that you know ${y = -8}$ , plug it back into $\thinspace {x = 2y+11}\thinspace$ to find $x$ ${x = 2}{(-8)}{ + 11}$ $x = -16 + 11$ ${x = -5}$ You can also plug ${y = -8}$ into $\thinspace {-4x+4y = -12}\thinspace$ and get the same answer for $x$ : ${-4x + 4}{(-8)}{= -12}$ ${x = -5}$